In the traditional furnace carbon black process, hydrocarbon feedstock is decomposed to carbon black and tail gas. The tail gas has combustible components (e.g. carbon monoxide and hydrogen), and non-combustible components (e.g. nitrogen, carbon dioxide and water). The carbon black is filtered from the tail gas and is dried in a natural gas fired rotary dryer with the combustion gases produced by burning the natural gas used as an inert atmosphere for the carbon black so that the carbon black will not oxidize during drying. The tail gas filtered from the carbon black is vented to the atmosphere.
The rising price of natural gas has prompted carbon black manufacturers to try to find ways of utilizing the heat content of tail gas. In one process, the filtered tail gas is dehumidified to increase its heat content and is used to replace at least some of the natural gas used to dry the carbon black. This results in significant savings, but the carbon black so produced is no longer useful in certain applications. For instance, carbon black dried using the waste heat from the tail gas caused bubbles in the low density polyethylene extrudants containing such carbon blacks.